A rocky debut for US home security firm ADT. Shares in the company fell as much as 13.9 per cent to $12.06 on its first day of trading on Friday, less than two years after private equity owner Apollo acquired the business via a massive leveraged buyout.

The lurch lower is another setback for ADT, which already had to price its initial public offering below its target range after selling fewer shares than planned. The company, which provides alarm systems and security monitoring services to homes and businesses, priced its shares at $14 a piece, below the original target range of $17-$19.